On Fri, 23 May 2008 04:52:24 -0400, Doug
wrote:
On Tue, 20 May 2008 18:47:38 -0300, Paul M. Eldridge
wrote:
On Tue, 20 May 2008 15:38:12 -0400, Doug
wrote:
[...snip...]
To the original poster:
With Connecticut making a dumb experiment with electric rate
deregulation (as did California under Gov. Gray out Gray), electrical
rates have skyrocketed. Connecticut, except perhaps for Hawaii, now
has the highest rates in the nation. Don't even consider electric
heat.
Electric heat pumps are also generally a poor choice here in CT. There
are simply too many winter days that are cold enough to make the
backup electrical resistance heaters in the heat pump come on,
spinning your service meter and drving up your costs. Heat pumps only
are efficient down to about 35 degrees. Most CT winter days are below
that.
Doug
Hi Doug,
In an earlier reply to the OP, I recommended that she consider a
ductless heat pump to address her a/c needs and to help out with her
heating requirements as well. I also provided a link to the following
brochu
http://www.friedrich.com/downloads/D...s_Brochure.pdf
One of the models listed is the M24YF. It has a nominal cooling
capacity of 24,200 BTU/hr and in terms of heat output is rated at
27,600 BTU/hr at 47F and 21,000 BTU/hr at 17F. Thus, this two-ton
unit still provides nearly 90 per cent of its rated heat output at a
temperature well below freezing (this particular model operates down
to 5F).
The HSPF rating is 10.0 (Zone 4, which, if I'm not mistaken, includes
all of CT). In effect, it provides, on average, 2.94 kWh of heat for
every kWh consumed, so if the OP pays $0.18 per kWh, her effective
cost per kWh of heat over the span of the entire heating season is
just $0.061. At an AFUE of 82%, that works out to be the equivalent
of oil heat at $2.04 per gallon -- in this case, less than half the
going rate.
If the OP ultimately decides to keep her oil boiler, it makes good
sense to pay a few hundred dollars more for a mini-split that both
heats and cools; the incremental cost could be recaptured in as little
as one or two months.
If she switches to natural gas, then a ductless heat pump could still
make sense, even if is only used during periods of relatively mild
weather; again, the difference in cost between an a/c only system and
a heat pump is relatively modest and it's always a good idea to have a
backup source of heat in case the main system goes down for any
reason.
Then again, it might make sense to use it all winter long. According
to the DOE's most recent numbers, the average (six month) retail price
of natural gas in Connecticut is $1.766 per 100 CCF (roughly speaking,
100 CCF = 1 therm = 100,000 BTUs). A gas boiler with an AFUE of 86%
provides about 25.2 kWh of heat (net) so, on that basis, natural gas
costs about $0.07 per kWh(e). That means the seasonal operating costs
of aforementioned heat pump at $0.061 per kWh(e) are lower, even when
the homeowner pays $0.18 per kWh to their utility.
Cheers,
Paul
I'm a bit puzzled by the literature of that heat pump.
The electrical wattage for heating is over double that of cooling.
The compressor shouldn't draw any more when its cycle is reversed.
Is it that they are using an electrical strip heater when temp drops
in order to maintain output?
Doug
Hi Doug,
I'm looking at the specs for the M24YF (page 6 of this brochure) and
without the benefit of morning coffee I can't find where this is
printed. The only wattage I see listed is for cooling and this is
shown as 2.31 kW. Power consumption in heating mode is normally
slightly lower and will more or less follow heat output, so as heating
capacity starts to taper off with outdoor temperature, so too will
wattage. There are no backup strips in these units.
As I recall, my ductless unit (a 14,000 BTU/hr Friedrich, nee
Fujitsu), draws 1,290-watts in cooling mode/1,230-watts in heating
(nominal) and, again, as it gets colder the number of watts pulled
will dimmish.
Cheers,
Paul